Well, i just got a 05 STi, and my perrin downpipe just came in. I was wondering if it would be bad for my car if i put on the downpipe, and left the stock exhaust on... thanks

 

Not bad for the subie, but you wont get nearly as much power unless you replace the whole exhaust. If you are going to the trouble of removing your exhaust from the dp, might as well put something that will give you more boost on there. If your issue is stealth go for a stealthback. I got mine from Daddys SCP. I love the low profile sound and power output throughtout the power band but especially at wot.

www.daddysscp.com

 

You're going to get boost creep if you put that downpipe in without engine management.
The Vf39's(the current turbo that is in the STI) are known to have boost creep with a catless downpipe.
You may want to wait until you get some EM.

Here is some info on boost creep.
https://www.i-club.com/forums/engine-power-ej25t-sti-2006-wrx-90/why-did-do-boost-creep-44825/

 

Late 04's and all 05's are less prone to boost creep than the earlier 04's. But it is still a good idea to get engine management, if for no other reason than to free up additional hp.

 

isnt the perrin dp so pretty.....

 

just go with aps 3" tbe,no cats .you won't regret it.